To solve the problem of strengthen the noise resistance of encoded data and of reducing bit error rate, when it is decoded.

A GS-APP decoding portion 52 of a GS-decoding portion 50 receives apriori probability related to an information bit u, a parity bit p1 and a parity bit p2 sent from a turbo-decoding portion 60, calculates outside informations and sends them to the turbo-decoding portion 60, when it does a soft decision decoding of a receiving bit y. The outside informations are divided into the information bit u and the first parity bit p1 which are necessary for decoding at a first APP decoding portion 62 and into the second parity bit p2 necessary for decoding at a second APP decoding portion 64 by a demultiplexer 102. A normal turbodecoding is conducted at the turbo-decoding portion 60, and the outside informations calculated by the second APP decoding portion 64 is sent to the GS-decoding portion 50. By cooperation between the GS decoding portion 50 and the turbo-decoding portion 60, the reliability is increased and the bit error rate of the information bit u is decreased.